Bacteria, yeast and filamentous fungi, as well as specialized cells of plants, invertebrates and vertebrates express membrane proteins useful for the uptake of amino acids, dipeptides and tripeptides. Lubkowitz et al., Microbiology 143: 387-396 (1997); Hauser et al., Mol. Membr. Biol. 18(1): 105-112 (2001); Stacey et al., Trends Plant Sci. 7(6): 257-263 (2002); Rubio-Aliaga & Daniel, Trends Pharmacol. Sci. 23(9): 434-440 (2002). Transporters that also accept larger oligopeptides (4-5 amino acid residues) are known in yeast, filamentous fingi and plants. Protein digestion into amino acids has been investigated in microorganisms used in food fermentation industry. Bacteria of the genus Lactobacillus (O'Cuinn et al., Biochem. Soc. Trans. 27(4): 730-734 (1999)) and fungi of the genus Aspergillus (Doumas et al., Appl. Environ. Microbiol. 64: 4809-4815 (1998)) secrete endoproteases and exoproteases, which cooperate very efficiently in protein digestion.
Aminopeptidase activity, which may also play a role in the development of fungus during infection, has been detected in the mycelium and culture supernatant of a species of fungi (De Bersaques & Dockx, Arch. Belg. Dermatol. Syphiligr. 29: 135-140 (1973); Danew & Friedrich, Mykosen 23: 502-511 (1980)), however, no aminopeptidase or carboxypeptidase has been isolated and characterized from dermatophytes to date.